A typical lawn sweeper generally includes a brush assembly having a plurality of rotatable brushes driven by a pair of wheels that are in contact with the ground. The lawn sweeper is towed behind a lawn implement, causing the wheels and, in turn, the brushes to rotate. The brushes sweep yard clippings and other debris from an underlying ground surface into a hopper or bag located behind the brushes.
Although current lawn sweepers are generally effective, there is room for improvement. One drawback of current lawn sweepers relates to a tow bar of the sweeper which is connected by means of a hitch to a draw bar of an associated lawn implement, such as a tractor, mower, or all-terrain vehicle. When attached to the tractor the tow bar should be generally parallel to the ground. If the tow bar is not generally parallel to the ground the efficiency of the lawn sweeper may be adversely affected. For example, at one non-parallel extreme position of the tow bar the brushes of the lawn sweeper may not properly contact the ground, reducing the amount of material collected by the lawn sweeper. At another non-parallel extreme, components of the sweeper may drag along the ground, causing damage or premature wearout of sweeper components. Attempts have been made by others to provide an adjustable clevis to solve this problem, such as that disclosed by U.S. Pat. No. 6,640,532 issued to Bogart, et al. However, such adjustable devises typically comprise detachable components that must be aligned with openings of the tow bar and then secured to the tow bar with mounting hardware. The detachable components are subject to being lost which could render the lawn sweeper unusable. Adjustment of current clevis hitches with respect to the tow bar may also require the use of tools which can be inconvenient and time-consuming for the user.
Another shortcoming of current lawn sweepers relates to the rotating brushes. In particular, current designs typically employ a plurality of linear or straight brushes that are longitudinally attached to a rotating axle. A confronting edge of each brush contacts the ground generally along the full length of the brush when the brush assembly is rotating, causing relatively high transitory loading stresses to be placed upon the brush assembly and associated components, such as support structures and drive gears of the lawn sweeper. The high loading stresses tend to reduce the useful life of these devices.
Yet another area for improvement of current lawn sweeper designs is the height adjustment feature. This feature is important to the operation of the sweeper because the brush height must be adjusted for optimal performance under various conditions. For example, the optimum brush height for sweeping leaves from a grass lawn varies with the length of the grass. Likewise, the brush height for sweeping driveways or sidewalks may also differ from that used for sweeping grass. Generally, current lawn sweepers have some form of an adjustable friction control device, such as a knob, that may be loosened to allow the brush height to be adjusted, then re-tightened to hold the sweeper at the selected height. This type of system has several drawbacks. First, the knob and associated components, such as washers, screws and nuts, are subject to being lost if the knob vibrates loose during operation, which could render the sweeper unusable. The knob may also loosen during use and allow the brush height to change without the knowledge of the operator, thereby degrading the efficiency of the lawn sweeper and even potentially damaging the lawn sweeper. In addition, tightening the knob sufficiently so that it does not inadvertently loosen can be difficult because the operator is often required to hold the sweeper at the desired height while simultaneously tightening the knob.
There is a need for a lawn sweeper having an easily-adjustable hitch clevis whose components are less prone to loss. There is an additional need for a lawn sweeper having a more efficient brush assembly. Further, a need exists for a lawn sweeper having a height adjustment feature that is not prone to inadvertent loosening.